High-strain-rate superplasticity and microstructural evolution in ECAP-processed Mg-6.5Y-1.2Er-1.6Zn-0.5Ag alloy

A warm equal-channel angular pressing (ECAP) procedure was applied to a new Mg-6.5Y-1.2Er-1.6Zn (WEZ612)-0.5Ag alloy with a long-period stacking ordered (LPSO) phase. The microstructure, superplasticity, and deformation mechanism of the WEZ612-0.5Ag alloy were then systematically investigated. Three different precipitation phases formed in the alloy with trace Ag addition, namely LPSO, g, and nanoprecipitate phases. A remarkable elongation of 726% was attained at 623 K and a strain rate of 0.01 s-1. The strain rate sensitivity index (m) and activation energy (Q) under these deformation conditions were 0.461 and 133.08 kJ mol-1, respectively. These m and Q values confirm that the primary deformation mechanism of the WEZ612-0.5Ag alloy at 623 K was grain boundary sliding assisted by lattice diffusion. The highly stable LPSO phases, g precipitates, and nano -precipitates synergistically improved the superplasticity of the alloy by retarding crack propagation and grain growth and by promoting the basal plane slip. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

A warm equal-channel angular pressing (ECAP) procedure was applied to investigate the microstructure, superplasticity, and deformation mechanism of a Mg-6.5Y-1.2Er-1.6Zn (WEZ612)-0.5Ag alloy. The alloy exhibited remarkable elongation of 726% at 623 K and a strain rate of 0.01 s-1, with the primary deformation mechanism being grain boundary sliding assisted by lattice diffusion. This improvement in superplasticity was attributed to the presence of stable LPSO phases, g precipitates, and nano-precipitates, which hindered crack propagation and grain growth and promoted basal plane slip.